"There are sporadic artillery strikes and you can hear shooting in the town of Ras al-Ain," said Rami Abdul Rahman, head of the Syrian Observatory for Human Rights.
'Ankara got exactly what it wanted': Turkey agrees with US to pause Syria assault
He said both the Turkish military and its Syrian allies were involved in the fighting with the Kurdish-dominated Syrian Democratic Forces (SDF).
An AFP journalist on the Turkish side of the border heard artillery fire and saw clouds of smoke in several places inside Syrian territory.
Ras al-Ain has been a major goal of the Turkish offensive since its launch on October 9 but the town's Kurdish defenders have put up fierce resistance.
Turkey announced a 120-hour suspension of its offensive late on Thursday, and Abdul Rahman said there was a lull in fighting in much of the rest of northeastern Syria.
Pence announces ceasefire deal with Erdogan to end Turkey's Syria offensive
Under the deal reached after US Vice President Mike Pence flew to Ankara, Kurdish forces are required to withdraw from a border strip 32 kilometres (20 miles) deep, which will become the "safe zone" long sought by Turkey.
The SDF said they were "ready to abide by the ceasefire" in the border strip between Ras al-Ain and Tal Abyad.
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